On Mon, Sep 7, 2009 at 10:14 PM, Stephen Conrad<[email protected]> wrote: > So, I plugged in (via USB) my USB Hub and I plugged in 2 USB Thumb > Drives (a 2 GB and a 247 MB one (according to the Get Info command) > but when I tried to plug in a 3rd (512 MB drive) it gave me a Low > Power Warning.
If the question is how many devices can your hub support when it powered only by its connection to your computer, the answer would be "it depends" on what devices you plug into the hub. By spec, a single USB port (whether v1.1 or v2.0) can only be expected to provide a max of a 0.5 amp. So there is at most 0.5 amp of current available to run the hub and any other devices that you plug into the hub. Now if the devices you attach via the hub are all very low power, then this won't be a problem. But it appears that it takes more than a 1/2 amp of current to power the hub plus the 3 USB flash drives you tried. > the folks at Rat Shack (Radio Shack) said it can run off the USB bus > and I can use it with 4 thumb drives. Unless I'm missing something here, I think they are just plain wrong about that. The most common place people run into problems with the 1/2 amp restriction for a USB port is when they attempt to power a 2.5" drive from a single USB port. For some drives this is just not enough current to let the drive spin up. This is why they came up with the (slightly wacky) cables which let you plug the drive into two USB ports. One of the ports is used for both data and power while the 2'nd is used just for power. Supposedly you can get 1 amp of current if you combine two USB ports which should be enough for any 2.5" drive. If you want to ensure that you can use all four ports on your hub you'll either have to power the hub another way or use devices that require less current. No? -irrational john --~--~---------~--~----~------------~-------~--~----~ You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list -~----------~----~----~----~------~----~------~--~---
